1. Field of the Invention
The present invention relates to metal working lubricants and more specifically to a lubricating agent particularly but not exclusively for use in the cold rolling of metals such as steel, stainless steel, silicon steel or molybdenum steel.
2. Prior Art
Metals can be worked into desired shapes by rolling, drawing, pressing, cutting, reducing, ironing and similar working operations in which lubricants are selectively used to suit the particular application. Particularly in the manufacture of metallic sheets, there have been used two typical processes, i.e. a hot rolling and a cold rolling. A variety of lubricants have heretofore been proposed for the cold rolling of metals. Lubricants have been used even in the hot rolling of certain metals such as aluminum and its alloys. In the cold rolling operation, rolled sheets need in many cases to be subsequently annealed to prevent the sheet surfaces from being unduly hardened.
The following characteristics are those required for lubricants which may be used particularly in the cold rolling of metals.
(1) Good rolling efficiency, i.e. high oiliness and great oily film strength PA0 (2) Excellent cooling efficiency PA0 (3) Excellent glossing and mar resistance on finished metal surfaces PA0 (4) High heat stability and long service life PA0 (5) Uniform adherence to metal surfaces PA0 (6) Easy handling and economical feasibility PA0 (7) Oil stains or fouling reduced to absolute minimum PA0 (8) High corrosion resistance
A keen demand has been voiced for high speed cold rolling and hence increased productivity. However, such high speed operation would literally involve the generation of intense heat from friction and plastic deformation. Of the foregoing characteristics, therefore, cooling efficiency and heat stability are the most important for the cold metal working.
In the cold rolling of metals, mineral oils of low kinetic viscosity have been widely used for their superior cooling efficiency. Such mineral oils however have a drawback in that their flash point is rather low, meaning fire hazards.
In order to resolve this problem, mineral- or fat-type soluble oils have been developed from an oily material such as mineral oil of low kinetic viscosity, palm oil or beef tallow which is emulsified in water. These soluble oils take advantage of improved cooling efficiency and non-flammability owing to the presence of water. Eligible mineral-type soluble oils may be obtained for instance by mixing a mineral oil of low viscosity with an emulsifier and emulsifying the resulting mixture in water with stirring. This soluble oil however is still unsatisfactory as its lubricating capability is not sufficient and it often causes oil stain during annealing, because of the presence of various additives, particularly of a metal.
Fat-type soluble oils find wide application for their lubricating efficiency, but require repeated heating and agitation during metal working so as to maintain a uniformly emulsified condition. Furthermore, metallic products as finished require cleaning to prevent oil stain. For such cleaning, there are used alkalis, solvents, electrolytes and the like, but all this would entail added equipment and labor yet with inadequate results.